See, when u r rebooting an iPad, it follows a boot sequence in which only the Secure Enclave chip, a security enforcing chip right beside the main processor (in ur case, M3). When you long press the top power button, it shows a static Apple logo, a rapid relay race “The Secure Boot Chain” takes place. Electricity passes to the Secure Enclave, it verifies the cryptographic signatures for the authentic iPadOS software for the boot up, if it has been modified, even a teeny bit, by any developer, the Secure Boot Chain breaks, and the Secure Enclave refuses to boot up the iPad until Apple verifies it by the cryptographic signature for their specific device model and version.